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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 84 |
| 3 | 4208 |
| 4 | 386064 |
| 5 | 56523072 |
| 6 | 12121690944 |
| 7 | 3589856932608 |
| 8 | 1406019035808000 |
| 9 | 704535958463063040 |
| 10 | 439949357001315947520 |
| 11 | 335139715537167259791360 |
| 12 | 305989012726577998256148480 |
[1,4,84,4208,386064,56523072,12121690944, 3589856932608,1406019035808000,704535958463063040, 439949357001315947520,335139715537167259791360, 305989012726577998256148480] |